Nanofibers technology has hugely impacted both science and engineering disciplines. The motivations for the miniaturization process of polymers recline in producing nanosized fibers with superior properties (i.e., high mechanical properties and large surface area per unit mass) compared to micro fiber and film. The polymers functionalities plus the unique characteristics of nanofibers originated from being engineered in various forms have allowed nanofibers to be used in advance applications such as filtration, multifunctional membranes, composite reinforcement, tissue engineering scaffolds, wound dressings, drug delivery, artificial organs and vascular grafts, etc. nanofibers membranes, produced from synthetic and biopolymers have received attention due to their ease of fabrication and the ability to control their compositional, structural and functional properties. The key advantage in producing fibers is stored in their extremely small diameters, large surface-to-volume ratio, high porosity and superior mechanical performance.
Today, there is growing interest in developing natural low-cost alternatives to synthetic polymers (Crini et al., Prog. Polym. Sci., 2008, 33, 399-447). Of late, the most bountiful natural biopolymers chitin and chitosan, gelatin, etc., have become cynosure of all party because of an unusual combination of biocompatibility, low toxicity, low immunogenicity, and mechanical and physical properties as compared to synthetic polymers. However, applications of chitin are limited due to its inherent insoluble and intractable nature, whereas gelatin is not stable in aqueous solution and needs to be stabilized first to be used in the aqueous solution. chitosan ((1→4)-2-amino-2-deoxy-d-glucan and some traces of (1→4)-2-acetamido-2-deoxy-d-glucan) an alkaline hydrolytic derivative of chitin has better solubility profile, less crystallinity and is amenable to chemical modifications due to presence of functional groups as hydroxyl, amine, and acetamido. The chemical modification of chitosan is of interest because the modification would not change the fundamental skeleton of chitosan, would keep the original physicochemical and biochemical properties and finally would bring new or improved properties. Several chemical modifications such as oligomerization, alkylation, acylation, quaternization, hydroxyalkylation, carboxyalkylation, thiolation, sulfation, phosphorylation, enzymatic modifications and graft copolymerization along with many assorted modifications have been carried out. The chemical modification affords a wide range of derivatives with modified properties for specific end user applications in diversified areas mainly of pharmaceutical, biomedical and biotechnological fields. Assorted modifications, including chitosan hybrids with sugars, cyclodextrin, dendrimers, and crown ethers, have also emerged as interesting multifunctional, macromolecules. The versatility in possible modifications and the applications of chitosan derivatives presents a great challenge to scientific community and to industry. The successful acceptance of this challenge will change the role of chitosan from being a molecule in waiting to a lead player. Chitosan has been investigated by several researchers as a biosorbent for the capturing of dissolved hazardous organic and inorganic materials from aqueous solutions (Wan et al., React. Funct. Polym. 2008, 68, 1013-1051; Justus et al., Polymer, 2004, 45, 6285-6290). Its use as a biosorbent is justified by two important advantages: firstly, its low cost compared to commercial activated carbon (chitosan is derived by deacetylation of the naturally occurring biopolymer chitin which is the second most abundant polysaccharide in the world after cellulose); secondly, its outstanding chelation behavior (one of the major applications of this amino-polymer is based on its ability to tightly bind pollutants, in particular heavy metal ions and colored dyes).
Increase in the metal ions pollutions of water resources with industrialization has generated great concern in the last decade. Metal ions are not only toxic to human beings but also to animals and plants at very low concentrations.